We present the results of a two-point study of the topology and dynamics of high-altitude cusp regions under changing interplanetary magnetic field (IMF) direction. The study uses INTERBALL-1 and MAGION-4 measurements on April 2, 1996. An analysis of the MAGION-4 ion energy spectra indicates the presence of magneto sheath-like plasma well below the expected magnetopause position and a large region occupied by low-temperature dense plasma with the very low bulk velocity near the magnetopause. The examinations of two-point observations of the cusp-magnetosheath transition have confirmed our knowledge of the structure of a plasma entry region during stable IMF. Our study reveals a complicated topology of the magnetic field during cusp reformation from an initial to a final quasisteady state. We have found that such a reformation can take 10 - 15 minutes.
Simunek, J., Nemecek, A., & Safrankova, J. (2003). Configuration of the outer cusp after an IMF rotation. Advances in Space Research, 31(5), 1395–1400. Retrieved from http://www.sciencedirect.com/science/article/B6V3S-49BYTYR-1B/2/68022ef529ba82be497a7b20433e7037